research digest

Readings: Labor Intensive

Pregnant women today have access to much better medical advice and resources than their forebears - they aren't squeezing into Victorian-era "maternity corsets." But doctors still prescribe bed rest, warn against caffeine and alcohol, and forbid certain foods - often without offering supporting evidence. Emily Oster, associate professor of economics, questions conventional thinking in her new book, Expecting Better: Why the Conventional Pregnancy Wisdom is Wrong - and What You Really Need to Know. Oster explained in an interview how she applied her economics know-how to assess the literature on pregnancy.

Chicago Booth Magazine: What motivated you to write Expecting Better?

Emily Oster: The inspiration for the book was my own pregnancy. When I was expecting my daughter I was amazed at how little information was available - from my doctor or from existing pregnancy books - to help me make good decisions. Over and over again I faced some decision - whether to participate in prenatal testing, have a cup of coffee, or have an epidural - and I couldn't find the data to help me make it. In the end I went out to get this information for myself, and the book is my attempt to help empower other women to make the right pregnancy choices, while hopefully not spending every minute of their pregnancy doing research!

CBM: What are the challenges of finding good information about pregnancy?

Oster: Once I stopped buying every pregnancy book to see if it had the information I wanted, I realized that finding good information on pregnancy wasn't difficult - if I was willing to spend every weekend and many evenings reading the academic medical literature. The challenge is, first, finding these studies and, second, figuring out which are the good studies and which are the not-so-good ones. This is where my training as an economist came in. Empirical work in economics is very often focused on separating correlation and causation - does weight gain in pregnancy really cause your child to be obese later, or is it just that overweight women have overweight children because of lifestyle reasons? In the end, I found that many of the current pregnancy recommendations were based on studies that showed only correlation, not causation.

CBM: You challenge the notion that caffeine, alcohol, and other normally safe-in-moderation substances are taboo.

Oster: In the case of caffeine and alcohol I was struck by the inconsistencies in the recommendations. In the case of caffeine, even well-respected pregnancy books differ (two cups, three cups, or none). Most books will tell you "no alcohol," but many doctors (mine included) will say "oh, a few glasses of wine a week is fine." And restrictions on both of these are more relaxed in other countries. It seemed impossible that these different recommendations could all be right - and I figured there must be a real answer somewhere in the data.

CBM:Expecting Better is about what conventional pregnancy wisdom gets wrong. Does convention get anything right?

Oster: Of course! One obvious example is tobacco. Smoking during pregnancy is discouraged for good reason. It is dangerous for your fetus. Another, perhaps more obscure example is hot tubs, which should be avoided in the first trimester as there is pretty good evidence too much exposure leads to birth defects.

CBM: Has this book inspired you to do additional work on the subject?

Oster: Yes, I'm involved in research on why the United States has high infant mortality relative to Europe. And I'm also exploring methodology - introducing tools from economics to improve statistical inference in the public health literature.